US6066599A - High pressure oxidation of precursor alloys - Google Patents

High pressure oxidation of precursor alloys Download PDF

Info

Publication number
US6066599A
US6066599A US08469438 US46943895A US6066599A US 6066599 A US6066599 A US 6066599A US 08469438 US08469438 US 08469438 US 46943895 A US46943895 A US 46943895A US 6066599 A US6066599 A US 6066599A
Authority
US
Grant status
Grant
Patent type
Prior art keywords
silver
composite wire
filaments
oxide
metal oxide
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Fee Related
Application number
US08469438
Inventor
Alexander Otto
Lawrence J. Masur
Eric R. Podtburg
Kenneth H. Sandhage
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
American Superconductor Corp
Original Assignee
American Superconductor Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Grant date

Links

Images

Classifications

    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01LSEMICONDUCTOR DEVICES; ELECTRIC SOLID STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H01L39/00Devices using superconductivity; Processes or apparatus peculiar to the manufacture or treatment thereof or of parts thereof
    • H01L39/14Permanent superconductor devices
    • H01L39/143Permanent superconductor devices comprising high Tc ceramic materials
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10TTECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T29/00Metal working
    • Y10T29/49Method of mechanical manufacture
    • Y10T29/49002Electrical device making
    • Y10T29/49014Superconductor

Abstract

An unsegregated metal oxide/silver composite wire is provided having a plurality of metal oxide filaments disposed within a matrix comprising silver, wherein the filaments are comprised of at least copper, and an intermediate region comprising copper oxide and silver in contact with and surrounding each of the metal oxide filaments. The intermediate region has a thickness of no greater than three microns. Each of the metal oxide filaments extends continuously for the length of the wire, and each of the metal oxide filaments is separated from adjacent filaments by the matrix.

Description

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a divisional of application Ser. No. 08/082,093, filed Jun. 24, 1993, now U.S. Pat. No. 5,472,527, and this application is also a continuation-in-part of application Ser. No. 07/881,675, filed May 12, 1992, now U.S. Pat. No. 5,683,969.

FIELD OF THE INVENTION

This invention relates to high temperature superconducting oxide composites having unsegregated microstructures. In particular, the invention relates to high temperature oxide superconductor-metal composites prepared by high pressure oxidation of metallic precursors.

BACKGROUND OF THE INVENTION

Oxide superconductors have been prepared by oxidation of a precursor alloy which contains the constituent metallic elements of the oxide superconductor and the matrix metal (typically, primarily silver). The matrix metal must itself be inert to oxidation or "noble" under the oxidation conditions employed during the process. The heat treatment of the composite is preferably carried out in two steps. A first heat treatment is carried out at relatively low temperatures in order to oxidize the component precursor elements into simple metal oxides or "suboxides". Subsequent heat treatments are then carried out at higher temperatures to convert the suboxide phases into the superconducting oxide phase(s). By "suboxide" as that term is used herein, it is meant simple, binary and/or ternary oxides of the component metals of the superconducting oxide.

Despite the relatively rapid diffusion of oxygen through the silver matrix phase, full oxidation of the metallic components into suboxides (in a first thermal treatment) can require extremely long times (for example, 600 hours). During heating at elevated temperatures, the mobilities of the precursor elements and their cationic forms are enhanced. The precursor elements diffuse into the surrounding silver metal, thereby impairing the chemical and physical integrity of the composite. This has the effect of interfering with the formation of oxide superconductor composites with good physical and electrical properties.

By "precursor elements", as that term is used herein, it is meant the individual metallic elements of the precursor alloy or their cationic forms. Typically, the precursor elements diffuse as neutral species; however, cations are also expected to contribute, in varying degrees, to the mobility of the precursor elements. Copper has the highest mobility of the constituent precursor elements, but also barium in the yttrium-barium-copper-oxygen (YBCO) system, bismuth and/or lead in the bismuth(lead)-strontium-calcium-copper-oxide (BSCCO) system and thallium and/or lead in the thallium(lead)-strontium-calcium-copper-oxide (TlSCCO) system are known to diffuse into the silver matrix. It is expected that given sufficient time and appropriate reaction conditions, other elements will also have measurable mobilities in silver at a level sufficient to impair composite mechanical and electrical properties.

In particular, the ability of precursor elements to segregate during thermal treatment has made it difficult to prepare multifilamentary wires having high filament counts. By "multifilamentary wires", as that term is used herein, it is meant wire, rods, tapes and the like, containing oxide superconductor filaments within a matrix metal, where the filaments run axially parallel to one another along the length of the wire, the "longest dimension". By "high filament count", as that term is used herein, it is meant filament densities of greater than 10,000 filaments/cm2 as determined for a cross-section transverse to the longest dimension. At high filament densities, even the slightest segregation of precursor elements results in the coalescence of individual filaments and the deterioration of wire properties.

High oxygen pressure has been used in the internal oxidation of Sn--Ag alloys. Tanaka et al. in U.S. Pat. No. 5,078,810 (hereinafter, "Tanaka") observed that high pressure oxidation eliminated scale formation of tin oxides on the outer surface of the silver composite due to the diffusion of tin to the surface. Tanaka addresses the problem of tin migration to the composite surface and not the segregation of tin within the composite. Indeed, segregation such as that observed for complex oxide superconductor composites can not occur in the simple tin oxide-silver composites disclosed by Tanaka.

It is an object of the present invention to provide a low temperature oxidation process for preparation of a metal oxide which minimizes diffusion and segregation of the precursor elements into the silver phase without unfavorably affecting the oxidation time.

It is a further object of the invention to provide a low temperature oxidation process for preparation of an oxide superconductor which minimizes diffusion and segregation of the precursor elements into the silver phase without unfavorably affecting the oxidation time. The object of the present invention provides an oxide superconductor composite with improved properties, such as high critical current density.

It is a further object of the invention to provide an oxide superconductor multifilamentary composite wire characterized by a highly unsegregated microstructure and a high filament count.

SUMMARY OF THE INVENTION

The invention provides a method for making an unsegregated oxide superconductor silver composite. The invention also provides a multi-filamentary oxide superconductor-silver composite having an unsegregated microstructure and a high filament count. By "unsegregated" as that term is used herein, it is meant that little or none of the precursor elements have diffused away (or become segregated) from the precursor alloy region. Because diffusion occurs under oxidizing conditions, segregated precursor elements are identified as oxide phases enriched in segregated elements(s), i.e., CuO, PbO, Bi2 O3, etc., in the final metal oxide or oxide superconductor composite.

In one aspect of the present invention, an unsegregated metal oxide/silver composite is prepared by forming a precursor alloy comprising silver and precursor elements having the stoichiometry of a desired metal oxide and oxidizing the precursor alloy under conditions of high oxygen activity selected to permit diffusion of oxygen into silver while significantly restricting the diffusion of the precursor elements into silver, so that oxidation of the precursor elements to the desired metal oxide occurs before diffusion of the precursor elements into silver. For the purposes of the invention, "high oxygen activity" is defined as oxygen activity equivalent to the activity of pure oxygen in its gaseous form (O2) at a temperature greater than 200° C. and at a pressure greater than ambient.

According to the invention, an unsegregated oxide superconductor-silver composite is prepared by further heating the metal oxide-silver composite obtained as described hereinabove under conditions selected to convert the metal oxides into the desired oxide superconductor.

In preferred embodiments, the oxidation of the metal precursor to the metal oxide is carried out at a temperature in the range of 250-450° C., and more preferably 320-430° C. In preferred embodiments, high oxygen activity is attained using high oxygen pressure, oxygen-releasing gases or electromagnetic means. The high oxygen pressure ranges from above ambient to substantially the oxygen threshold pressure for the formation of silver oxide. The PO2 range is preferable 15-3000 psi, more preferably 800-3000 psi and most preferably 1200-1800 psi. In another preferred embodiment, the precursor alloy is oxidized at a temperature in the range of 200 to 450° C. and at an oxygen pressure in the range of 15 to 3000 psi.

In yet another preferred embodiment, a second gas is used to dilute the oxygen for enhanced total pressure above the desired oxygen pressure. Total gas pressures can range from 16 to 60,000 psi and the diluting gas may be any non-reactive gas, such as Ar, N2, He, Ne, Kr or Xe.

Another aspect of the invention provides for a dense (pore or void-free) oxide superconductor composite having a discrete oxide superconductor phase and a silver phase with little or no diffusion of precursor elements into the silver phase. "Little or no diffusion" is defined as having a metal oxide no more than a distance of three microns from the corresponding oxide superconducting phase. An oxide superconductor composite is characterized as having a microstructure in which a cross-section transverse to a longest dimension consists of the silver matrix and a clearly defined oxide superconductor regions having a density of oxide regions of at least 10,000 regions/cm2.

Yet another aspect of the invention provides for a dense (pore or void-free) metal oxide composite having a discrete metal oxide phase and a silver phase with little or no diffusion of precursor elements into the silver phase. "Little or no diffusion" is defined as having a metal oxide no more than a distance of three microns from the corresponding metal oxide phase. A metal oxide composite is characterized as having a microstructure in which a cross-section transverse to a longest dimension consists of the silver matrix and clearly defined metal oxide regions having a density of oxide regions of at least 10,000 regions/cm2.

The method of the present invention, prevents "loss" of the desired metal oxide phase due to diffusion of particular precursor elements into the silver matrix by dramatically reducing precursor element mobilities during processing. Conversion of the precursor elements to the final oxide superconductor is more complete, since off-stoichiometry in the precursor oxide phase is greatly reduced. Further, texturing of the oxide superconductor phase is more efficient when residual blocky precursor oxide phases (typically formed due to off-stoichiometry in the starting precursor oxide) have been eliminated.

BRIEF DESCRIPTION OF THE DRAWING

In the Drawing:

FIG. 1 is a plot of difflsivity of oxygen and copper into silver as a function of temperature;

FIG. 2 is an optical photomicrograph of a multifilamentary YBa2 Cu4 Ox oxide superconductor-silver composite oxidized at (a) high temperature and ambient oxygen pressure, and (b) low temperature and high oxygen pressures for the same amount of time; and

FIG. 3 is a plot of extent of oxidation v. time at several temperatures and for two different pressure regimes.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention provides a method for oxidizing a precursor alloy to optimize the competing effects of oxidation time and precursor element mobility. The precursor elements are immobilized without significantly extending and, in some cases, even reducing the oxidation time.

Segregation occurs by migration of the precursor elements of the alloy into the silver matrix, where they are oxidized to form the corresponding metal oxides. Once formed, the cations of the metal oxides can no longer diffuse readily through the silver matrix. However, because the segregated cations are not present in the proper stoichiometry to form the desired metal oxide or oxide superconductor when subjected to subsequent thermal treatments under conditions favorable to the desired oxide formation, the cations remain as particles surrounding the newly formed desired oxide phase (see, FIG. 2).

The faster the low temperature thermal treatment is completed, the less time the precursor elements have to diffuse into the silver matrix and the extent of segregation is therefore reduced. However, the mass transport rate of the oxygen through the silver must be increased without altering the transport rates of the precursor elements if significant precursor element segregation is to be avoided. The increased mass transport rate of oxygen can be accomplished by increasing the oxygen activity of the system. Hence, unsegregated metal oxide composites may be achieved by a thermal process at "low" temperatures in combination with conditions of high oxygen activity.

At sufficiently low temperatures, the precursor elements of the alloy are effectively prevented from travelling any significant distance through the matrix in the time it takes to fully oxidize the composite. This is possible because the diffusion rate of oxygen through the silver is less dependent upon temperature than the diffusion rate of precursor elements. FIG. 1 illustrates the temperature dependences of copper and oxygen diffusion through silver using a plot of diffusion distance v. temperature. The diffusion distance, x, of the ordinate represents the distance the element of interest has diffused into a silver matrix after a period of 10 hours under ideal conditions. It is clear from FIG. 1, that all diffusion rates increase with increasing temperature and the curve form is exponential. Note that the diffusion of oxygen into silver uses the millimeter (mm) scale for the ordinate, while the diffusion of copper into silver uses the micrometer (μm) scale for the ordinate. However, the diffuision of copper into silver (represented by curve 10) has a more rapidly increasing exponential form than that of oxygen into silver (represented by curve 12). Hence, the distance diffused by copper into silver increases very rapidly as temperature increases, in particular, at a temperature greater than approximately 400 to 430° C. Hence, diffusion of the precursor elements can be effectively halted by holding the oxidation temperature below the temperature at which diffusion increases at a rapid rate, i.e., less than approximately 450° C.

To compensate for the reduced diffusivity of oxygen at the lower oxidation temperatures, the oxygen activity of the system is increased. Diffusivity of the precursor elements of the alloy and oxygen is PO2 independent. However, an increase in oxygen pressure increases the amount of oxygen that is dissolved in the silver matrix and thereby the flux of oxygen through silver is increased. This has the effect of increasing the mass transport of oxygen through silver, while the diffusivity (and mass transport) of the precursor elements is unaffected.

In a preferred embodiment, the oxidation temperature range for a precursor alloy is 200° C. to 450° C. In particular, precursors to bismuth(lead)-strontium-calcium-copper-containing oxide superconductors have thermal treatment temperatures in the range of 360° C. to 430° C. Precursors to thallium(lead)-strontium-calcium-copper-containing oxide superconductors have thermal heat treatment temperatures in the range of 200° C. to 450° C. The thermal heat treatment temperature is in the range of 300° C. to 350° C. for the precursors to rare earth-barium-copper-containing oxide superconductors.

The selected temperature ranges described hereinabove have the additional benefit in that they are below the recrystallization temperature of silver (Tcrystal) in most instances. The grain structure of silver influences the mass transport of oxygen. If the temperature of oxidation is below the recrystallization temperature of silver (˜200-400° C.), the silver matrix retains its fine-grained structure (assuming it is fine grained at the onset). It is then possible for oxygen to be transported along the silver grain boundaries. Hence, oxygen transport is enhanced in fine grained silver matrices by oxidation below the recrystallization temperature of silver.

The present invention calls for high oxygen activity. The requisite "high oxygen activity" for the present invention is equivalent to the activity of pure oxygen in its gaseous form (O2) in the temperature range of 250° C. to 450° C. and at pressures in the range of 15 psi to 3000 psi. This can be accomplished in a number of ways, for example by using high oxygen pressure (PO2), or by using activated forms of oxygen, generated, for example, by oxygen-releasing gases or electromagnetic means.

Oxygen-releasing gases are known in the art and include, but are in no way limited to, ozone, NOx, and the like. Electromagnetic means include high frequency radiation, such as microwave radiation, which are capable of generating reactive forms of oxygen. Anodization is another known way to generate reactive oxygen species.

In a preferred embodiment, high oxygen pressure is used as the high oxygen activity means. The rate of oxidation of the precursor elements increases as oxygen pressure increases up to a maximum rate corresponding to the onset of extensive silver oxide formation at the outer surface of the silver composite ("threshold pressure"). Oxidation rates are substantially independent of oxygen pressure beyond this point (threshold pressure of silver oxide formation). The threshold pressure will vary with temperature. For example, the threshold pressure is 1500 psi at 400° C. At lower temperatures, the threshold pressure of silver oxide decreases. For example, a threshold pressure of 300 psi at 330° C. is typical. It is desirable but not necessary to operate at oxygen pressures at or near the threshold pressures. It is also possible to operate at oxygen pressures above the threshold pressures. The oxygen pressure preferably is in the range of 15 psi to 3000 psi, more preferably in the range of 800-3000 psi and most preferably in the range of 1200-1800 psi.

In another preferred embodiment, the total gas pressure can range up to 60,000 psi. The oxygen pressure will still be in the preferred ranges described above; however, it is diluted with a second gas to enhance the total pressure of the system. The diluting gas may be any non-reactive gas, such as Ar, N2, He, Ne, Kr or Xe. The addition of the diluting gas will affect the total oxygen activity and a slightly greater oxygen pressure may be needed in the mixed gas system for oxygen activity comparable to the oxygen-only system. In preferred embodiments, the alloy is oxidized at an oxygen pressure in the range of 800-3000 psi and a total gas pressure of 801-60,000 psi with a second gas used to dilute the oxygen for enhanced total pressure above the desired oxygen pressure. In other embodiments, the alloy may be oxidized at an oxygen pressure in the range of 1200-1800 psi and a total gas pressure of 1201-60,000 psi with a second gas used to dilute the oxygen for enhanced total pressure above the desired oxygen pressure. Enhanced total pressure is useful to prevent local strain/stress splitting of the oxide superconducting grains which may occur due to the volume change associated with oxidation.

Typically, the multifilamentary oxide composites of the invention take the form of a silver wire, ribbon or tape. A multifilamentary composite such as that shown in FIG. 2 is prepared in the following manner. The tape is formed by introducing finely divided precursor elements into a silver can and extruding the powder filled can into a wire of much smaller diameter. A number of extruded wires are then grouped together and co-extruded to form a wire having a plurality of metallic precursor filaments therein. Regrouping and co-extruding can be continued until the desired number of filaments are obtained. Tapes having filament counts of 100-2,000,000 have been prepared.

The method of the invention is described in the following experiment, with reference to FIG. 2. FIGS. 2a and 2b show a cross-sectional view of a YBa2 Cu4 Ox -silver composite containing multiple filaments of metal oxide in a silver matrix. In the figure, dark areas 20 represent the oxide superconductor phase and light areas 22 represent silver phase.

Bundles of six silver-precursor alloy composite multifilamentary tapes are placed in a pressure vessel with a 0.25" (0.635 cm) bore and purged by two "pressurize and drain cycles" at ambient pressure. The tapes are 0.10"×0.02" (0.254 cm×0.0508 cm) in cross section and 1" (2.54 cm) long. They contain 2527 filaments of copper-sheathed YBa2 alloy filaments with a precursor element stoichiometry of Y1 Ba2 Cu4 and a precursor element fill factor of 10 vol %. Each bundle is heated to 320° C. (at about 2000 psi oxygen pressure) by inserting the pressure vessel into the hot zone of a preheated furnace. The samples are heated for 10 to 20 h, and then are withdrawn from the furnace and air cooled. The samples are fully oxidized after 10 to 20 h. This is more than an order of magnitude faster than the required time for full oxidation at ambient pressure.

A polished cross section of the tape is examined by optical microscopy. The fully oxidized sample at 320° C. shows no discernable copper diffusion and the precursor geometry is preserved throughout the composite. Samples processed according to the method described hereinabove have been tested for superconductivity and found to have an onset of zero resistance at a temperature of 82 K.

A lead doped Bi-2223 oxide superconductor is processed in the following manner. A lead doped Bi-2223 precursor alloy powder is made by mechanical alloying the elements with up to 50 volume percent silver. The alloy powder is packed into a silver can and deformed repeatedly. A number of extruded wires are then grouped together and co-extruded to form a tape having a plurality of metallic precursor filaments therein. Regrouping and co-extruding can be continued until the desired number of filaments are obtained, yielding the multifilamentary precursor alloy silver matrix composite tape with a typical cross-sectional dimension of 0.75 mm×3.8 mm. A tape with 259 filaments and a precursor element fill factor equivalent of 15 volume percent is oxidized at 400° C. in 2.9 ksi oxygen for 300 hours for full oxidation with effectively no segregation of the precursor elements from the filaments.

FIG. 2 illustrates the improvement in composite microstructure arising from the method of the invention employing both a lower temperature and a higher than ambient oxygen pressure. FIG. 2a is a photomicrograph of a conventionally processed composite cross-section (containing 2527 filaments) that has been oxidized at 600° C. for 200 hours at ambient oxygen pressures. The boundary between the metal oxide regions and the silver matrix is poorly defined due to the high degree of diffusion of metallic elements (primarily Cu as CuO) in the silver matrix. In comparison, FIG. 2b is a photomicrograph of a composite cross-section (containing 2527 filaments) that has been oxidized at 340° C. for 200 h in 2000 psi oxygen. The boundary between the circular regions of the metal oxide and the silver matrix are much more clearly defined. The intrusion of the metal oxide into the silver is effectively eliminated in the composite of FIG. 2b subjected to the low temperature/high oxygen pressure thermal treatment of the present invention.

FIG. 3 is a plot of the extent of oxidation v. time at two oxygen pressures, ambient and 2000 psi, for Y1 Ba2 Cu4 Ox composite samples. Full oxidation is indicated by an extent of oxidation equal to 1. The rate of oxidation increases by approximately one order of magnitude for an oxygen pressure increase from ambient to 2000 psi, as evidenced by comparison of curve 30 (400° C., 14.7 psi) to curve 32 (400° C., 2000 psi) in FIG. 3. Although oxidation rate decreases with decreasing temperature, the increase in oxygen pressure can more than compensate for the temperature-induced rate decrease as illustrated by the comparable slopes for curve 30 (400° C., 14.7 psi) and curve 34 (320° C., 2000 psi). While a high temperature, high pressure thermal treatment such as that of curve 36 (470° C., 2000 psi) affords rapid oxidation, the extent of segregation is still considerable and not acceptable for superconducting applications. The resulting microstructure is not optimal because the higher temperature has not permitted an immobilization of the precursor elements. The best improvement in segregation is achieved by lowering the oxidation temperature while employing a high oxygen activity (here, pressure).

Once the metal oxide-silver composite is formed, it may be further heat treated using techniques known in the art to prepare an oxide superconductor. For example, the method can be applied to the preparation of all oxide superconductors, including but not limited to, YBa2 Cu3 Ox, wherein x is sufficient to provide an oxide superconductor having a Tc greater than 77 K; YBa2 Cu4 Ox, wherein x is sufficient to provide an oxide superconductor having a Tc greater than 77 K; (Bi,Pb)2 Sr2 Ca2 Cu3 Ox, wherein x is sufficient to provide an oxide superconductor having a Tc greater than 100 K, (Bi,Pb)2 Sr2 Ca1 Cu2 Ox wherein x is sufficient to provide an oxide superconductor having a Tc greater than 77 K, Hg1 Ba2 Ca2 Cu3 Ox, wherein x is sufficient to provide an oxide superconductor having a Tc greater than 100 K, Hg1 Ba2 Ca1 Cu2 Ox, wherein x is sufficient to provide an oxide superconductor having a Tc greater than 100 K, Hg1 Ba2 Cu1 Ox, wherein x is sufficient to provide an oxide superconductor having a Tc greater than 77 K, wherein x is sufficient to provide an oxide superconductor having a Tc greater than 100 K, (Tl,Pb)1 Sr2 Ca1 Cu2 Ox ; wherein x is sufficient to provide an oxide superconductor having a Tc greater than 100 K; and (Tl,Pb)1 Sr2 Ca2 Cu3 Ox, wherein x is sufficient to provide an oxide superconductor having a Tc greater than 100 K. Addition of other elements in small quantities to these oxide compositions do not alter the scope or spirit of the invention. The above oxide compositions are nominal; slight deviations therefrom are within the scope of the invention.

As the precursor elements are effectively immobilized as cation components of metal oxides, higher temperature processes can be employed without further segregation. For example, the metal oxide-silver composite is heated at 0.075 atm oxygen at 780° C. for 10 h, held at 815° C. for 50 h and then cooled to form the oxide superconductor, Bi2 Sr2 Ca2 Cu3 Ox (2223-BSCCO). Similarly, the metal oxide-silver composite is heated at 1.0 psi oxygen at 900° C. for 50 h, held at 450° C. for 100 h and then cooled to form the oxide superconductor, YBa2 Cu3 Ox (123-YBCO).

The composites of the present invention are characterized by their uniquely unsegregated composite microstructure and high filament count. For example, the silver matrix contains no oxide beyond a distance of 3 μm from the interface of the bulk oxide phase (metal oxide or oxide superconductor) and the silver matrix. Expressed in different terms, the oxide-silver composite has a microstructure in which a cross-section transverse to the longest dimension consists of a silver matrix and a clearly defined oxide (metal oxide or oxide superconductor) region having a density of oxide regions of at least 10,000 regions/cm2. Densities of well over 32,000 regions/cm2 up to 1,500,000 regions/cm2 have been observed without any degradation of electrical and mechanical properties. In order for densities on this scale to occur without impairment of the electronic and mechanical properties of the composite, little or no segregation must occur between neighboring filaments.

Other embodiments of the invention will be apparent to the skilled in the art from a consideration of this specification or practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with the true scope and spirit of the invention being indicated by the following claims.

Claims (9)

What is claimed is:
1. A multifilamentary composite wire, comprising:
a plurality of metal oxide filaments disposed within a matrix comprising silver, said silver matrix substantially free of copper oxide (CuO), and said filaments comprised of at least copper; and
an intermediate region comprising a diffused mixture of copper oxide (CuO) and silver in contact with and surrounding each of the metal oxide filaments, said region having a thickness of no greater than about three microns,
wherein each of the metal oxide filaments extends continuously for the length of the wire, and each of the metal oxide filaments is separated from adjacent filaments by the matrix.
2. The composite wire of claim 1, wherein the metal oxide comprises an oxide superconductor.
3. The composite wire of claim 1 or 2, wherein the composite wire comprises at least 2527 metal oxide filaments.
4. The composite wire of claim 1, wherein the composite wire is characterized by a filament density of 10,000 filaments per square centimeter of transverse cross-sectional area of the composite wire.
5. The composite wire of claim 1, wherein the composite wire is characterized by a filament density of 32,000 filaments per square centimeter of transverse cross-sectional area of the composite wire.
6. The composite wire of claim 1, wherein the composite wire is characterized by a filament density of 1,500,000 filaments per square centimeter of transverse cross-sectional area of the composite wire.
7. The composite wire of claim 1, wherein the silver of the matrix which is located greater than 3 microns from each said metal oxide filament is free from copper oxide.
8. The composite wire of claim 2, wherein the oxide superconductor is selected from the group consisting of YBa2 Cu3 Ox, YBa2 Cu4 Ox, (Bi,Pb)2 Sr2 Ca2 Cu3 Ox, (Bi,Pb)2 Sr2 Ca1 Cu2 Ox, Hg1 Ba2 Ca2 Cu3 Ox, Hg1 Ba2 Ca1 Cu2 Ox, Hg1 Ba2 Cu1 Ox, (Tl,Pb)2 Sr2 Ca2 Cu3 Ox, and (Tl,Pb)2 Sr2 Ca2 Cu3 Ox, where X is sufficient to provide an oxide superconductor having a Tc greater than 77K.
9. The composite wire of claim 1, wherein the metal oxide comprises oxides of two or more metals.
US08469438 1992-05-12 1995-06-06 High pressure oxidation of precursor alloys Expired - Fee Related US6066599A (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
US07881675 US5683969A (en) 1992-05-12 1992-05-12 Strongly-linked oxide superconductor and a method of its manufacture
US08080820 US5332990A (en) 1992-07-17 1993-06-24 High-frequency safety fuse
US08469438 US6066599A (en) 1992-05-12 1995-06-06 High pressure oxidation of precursor alloys

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US08469438 US6066599A (en) 1992-05-12 1995-06-06 High pressure oxidation of precursor alloys

Related Parent Applications (2)

Application Number Title Priority Date Filing Date
US07881675 Continuation-In-Part US5683969A (en) 1992-05-12 1992-05-12 Strongly-linked oxide superconductor and a method of its manufacture
US08082093 Division US5472527A (en) 1993-06-24 1993-06-24 High pressure oxidation of precursor alloys

Publications (1)

Publication Number Publication Date
US6066599A true US6066599A (en) 2000-05-23

Family

ID=26763976

Family Applications (1)

Application Number Title Priority Date Filing Date
US08469438 Expired - Fee Related US6066599A (en) 1992-05-12 1995-06-06 High pressure oxidation of precursor alloys

Country Status (1)

Country Link
US (1) US6066599A (en)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6202287B1 (en) * 1996-01-18 2001-03-20 American Superconductor Corporation Method for producing biaxially aligned super conducting ceramics
US6311385B1 (en) * 1998-04-28 2001-11-06 Sumitomo Electric Industries, Inc. High temperature oxide superconducting wire and method of manufacturing thereof
US6393690B1 (en) * 1995-05-19 2002-05-28 American Superconductor Corpration Structure and method of manufacture for minimizing filament coupling losses in superconducting oxide composite articles
US6448501B1 (en) * 1998-03-30 2002-09-10 Mcintyre Peter M. Armored spring-core superconducting cable and method of construction
US20030134749A1 (en) * 2001-06-22 2003-07-17 Fujikura Ltd. Oxide superconducting conductor and its production method
US20030226677A1 (en) * 1999-09-07 2003-12-11 Utilx Corporation Flow-through cable
US20040238886A1 (en) * 2002-01-08 2004-12-02 Jae-Gab Lee Thin film transistor array panel and a method for manufacturing the same
US20070062713A1 (en) * 2005-09-12 2007-03-22 John Szurpicki Rotary lawn edger tool

Citations (23)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS63225413A (en) * 1987-03-13 1988-09-20 Toshiba Corp Manufacture of compound superconductive wire
US4826806A (en) * 1986-07-31 1989-05-02 Shin Nisso Kako Co., Ltd. Fluoran compounds and color forming recording materials using same
US4929596A (en) * 1987-07-24 1990-05-29 Asea Brown Boveri Ag Process for producing a multiple-filament oxide superconductor
US4952554A (en) * 1987-04-01 1990-08-28 At&T Bell Laboratories Apparatus and systems comprising a clad superconductive oxide body, and method for producing such body
US4959279A (en) * 1989-01-17 1990-09-25 The Furukawa Electric Co., Ltd. Superconducting wire containing multifilamentary superconducting alloy
US4962085A (en) * 1988-04-12 1990-10-09 Inco Alloys International, Inc. Production of oxidic superconductors by zone oxidation of a precursor alloy
US4977039A (en) * 1989-03-27 1990-12-11 Agency Of Industrial Science And Technology Superconducting wire and cable
US4988669A (en) * 1988-07-05 1991-01-29 Asea Brown Boveri Ltd. Electrical conductor in wire or cable form composed of a sheathed wire or of a multiple-filament conductor based on a ceramic high-temperature superconductor
US5034373A (en) * 1989-12-22 1991-07-23 Inco Alloys International, Inc. Process for forming superconductor precursor
US5078810A (en) * 1990-02-08 1992-01-07 Seiichi Tanaka Method of making Ag-SnO contact materials by high pressure internal oxidation
US5088183A (en) * 1990-05-01 1992-02-18 Kanithi Hem C Process for producing fine and ultrafine filament superconductor wire
US5122507A (en) * 1987-05-01 1992-06-16 Sumitomo Electric Industries, Ltd. Process for manufacturing a superconducting composite
US5132278A (en) * 1990-05-11 1992-07-21 Advanced Technology Materials, Inc. Superconducting composite article, and method of making the same
US5189260A (en) * 1991-02-06 1993-02-23 Iowa State University Research Foundation, Inc. Strain tolerant microfilamentary superconducting wire
US5206211A (en) * 1989-03-31 1993-04-27 Asea Brown Boveri Ltd. Process for the production of an elongate body consisting of longitudinally aligned acicular crystals of a superconducting material
US5259885A (en) * 1991-04-03 1993-11-09 American Superconductor Corporation Process for making ceramic/metal and ceramic/ceramic laminates by oxidation of a metal precursor
US5304534A (en) * 1989-11-07 1994-04-19 The United States Of America As Represented By The United States Department Of Energy Method and apparatus for forming high-critical-temperature superconducting layers on flat and/or elongated substrates
US5347085A (en) * 1991-02-07 1994-09-13 The Furukawa Electric Co., Ltd. Multifilamentary oxide superconducting wires and method of manufacturing the same
US5395821A (en) * 1992-10-30 1995-03-07 Martin Marietta Energy Systems, Inc. Method of producing Pb-stabilized superconductor precursors and method of producing superconductor articles therefrom
US5472527A (en) * 1993-06-24 1995-12-05 American Superconductor Corporation High pressure oxidation of precursor alloys
US5516753A (en) * 1993-12-28 1996-05-14 Sumitomo Electric Industries, Ltd. Multifilamentary oxide superconducting wire and coil formed by the same
US5531015A (en) * 1994-01-28 1996-07-02 American Superconductor Corporation Method of making superconducting wind-and-react coils
US5683969A (en) * 1992-05-12 1997-11-04 American Superconductor Corporation Strongly-linked oxide superconductor and a method of its manufacture

Patent Citations (28)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4826806A (en) * 1986-07-31 1989-05-02 Shin Nisso Kako Co., Ltd. Fluoran compounds and color forming recording materials using same
JPS63225413A (en) * 1987-03-13 1988-09-20 Toshiba Corp Manufacture of compound superconductive wire
US4952554A (en) * 1987-04-01 1990-08-28 At&T Bell Laboratories Apparatus and systems comprising a clad superconductive oxide body, and method for producing such body
US5122507A (en) * 1987-05-01 1992-06-16 Sumitomo Electric Industries, Ltd. Process for manufacturing a superconducting composite
US5424282A (en) * 1987-05-01 1995-06-13 Sumitomo Electric Industries, Ltd. Process for manufacturing a composite oxide superconducting wire
US5338721A (en) * 1987-05-01 1994-08-16 Sumitomo Electric Industries, Ltd. Process for manufacturing a superconducting composite
US5169831A (en) * 1987-05-01 1992-12-08 Sumitomo Electric Industries, Ltd. Process for manufacturing a superconducting composite
US5043320A (en) * 1987-07-24 1991-08-27 Asea Brown Boveri Ag Process for producing a sheathed wire composed of a ceramic high-temperature superconductor
US4929596A (en) * 1987-07-24 1990-05-29 Asea Brown Boveri Ag Process for producing a multiple-filament oxide superconductor
US4962085A (en) * 1988-04-12 1990-10-09 Inco Alloys International, Inc. Production of oxidic superconductors by zone oxidation of a precursor alloy
US4988669A (en) * 1988-07-05 1991-01-29 Asea Brown Boveri Ltd. Electrical conductor in wire or cable form composed of a sheathed wire or of a multiple-filament conductor based on a ceramic high-temperature superconductor
US4959279A (en) * 1989-01-17 1990-09-25 The Furukawa Electric Co., Ltd. Superconducting wire containing multifilamentary superconducting alloy
US4977039A (en) * 1989-03-27 1990-12-11 Agency Of Industrial Science And Technology Superconducting wire and cable
US5206211A (en) * 1989-03-31 1993-04-27 Asea Brown Boveri Ltd. Process for the production of an elongate body consisting of longitudinally aligned acicular crystals of a superconducting material
US5304534A (en) * 1989-11-07 1994-04-19 The United States Of America As Represented By The United States Department Of Energy Method and apparatus for forming high-critical-temperature superconducting layers on flat and/or elongated substrates
US5034373A (en) * 1989-12-22 1991-07-23 Inco Alloys International, Inc. Process for forming superconductor precursor
US5078810A (en) * 1990-02-08 1992-01-07 Seiichi Tanaka Method of making Ag-SnO contact materials by high pressure internal oxidation
US5088183A (en) * 1990-05-01 1992-02-18 Kanithi Hem C Process for producing fine and ultrafine filament superconductor wire
US5132278A (en) * 1990-05-11 1992-07-21 Advanced Technology Materials, Inc. Superconducting composite article, and method of making the same
US5189260A (en) * 1991-02-06 1993-02-23 Iowa State University Research Foundation, Inc. Strain tolerant microfilamentary superconducting wire
US5330969A (en) * 1991-02-06 1994-07-19 Iowa State University Research Foundation, Inc. Method for producing strain tolerant multifilamentary oxide superconducting wire
US5347085A (en) * 1991-02-07 1994-09-13 The Furukawa Electric Co., Ltd. Multifilamentary oxide superconducting wires and method of manufacturing the same
US5259885A (en) * 1991-04-03 1993-11-09 American Superconductor Corporation Process for making ceramic/metal and ceramic/ceramic laminates by oxidation of a metal precursor
US5683969A (en) * 1992-05-12 1997-11-04 American Superconductor Corporation Strongly-linked oxide superconductor and a method of its manufacture
US5395821A (en) * 1992-10-30 1995-03-07 Martin Marietta Energy Systems, Inc. Method of producing Pb-stabilized superconductor precursors and method of producing superconductor articles therefrom
US5472527A (en) * 1993-06-24 1995-12-05 American Superconductor Corporation High pressure oxidation of precursor alloys
US5516753A (en) * 1993-12-28 1996-05-14 Sumitomo Electric Industries, Ltd. Multifilamentary oxide superconducting wire and coil formed by the same
US5531015A (en) * 1994-01-28 1996-07-02 American Superconductor Corporation Method of making superconducting wind-and-react coils

Non-Patent Citations (12)

* Cited by examiner, † Cited by third party
Title
"Etude Diffractometrique de la Dissolution de L'Oxygene dans le Niobium a Pression Moyenne (75 Torr) et Entre 300 et 400° C." C. Perrin et al., Journal of the Less-Common Metals 77, 49-59 (1981) (No Month).
"High Temperature Behaviour of Platinum Group Metals in Oxidizing Atmospheres" H. Jehn, Journal of the Less-Common Metals 100, 321-339 (1984) (No Month).
"High-Pressure Oxidation of Refractory Metals -Experimental Methods and Interpretation" W.M. Fassel, Jr. et al., 2 Metalkde, 64(4) 286-295 (1973) (No Month).
"The Internal Oxidation of Silver Alloys at High Pressures and in Atomic Oxygen" D. Stockel et al. AFSC Oxidation of Tengsten and other Refractory Metals, ML-TR-64-162 (Apr. 1965).
Etude Diffractometrique de la Dissolution de L Oxygene dans le Niobium a Pression Moyenne (75 Torr) et Entre 300 et 400 C. C. Perrin et al., Journal of the Less Common Metals 77, 49 59 (1981) (No Month). *
High Pressure Oxidation of Refractory Metals Experimental Methods and Interpretation W.M. Fassel, Jr. et al., 2 Metalkde, 64(4) 286 295 (1973) (No Month). *
High Temperature Behaviour of Platinum Group Metals in Oxidizing Atmospheres H. Jehn, Journal of the Less Common Metals 100, 321 339 (1984) (No Month). *
Mukai et al, "Multifilamentary Bismuth(2223) Multilayer-Wound Conductors for Power Transmission Lines," Materials Research Society, San Francisco, CA (Apr. 27-May 1, 1992).
Mukai et al, Multifilamentary Bismuth(2223) Multilayer Wound Conductors for Power Transmission Lines, Materials Research Society, San Francisco, CA (Apr. 27 May 1, 1992). *
Sato et al, "High-Jc Silver-Sheathed Bi-Based Superconducting Wires," IEEE Trans. on Magntics 27(2) 1231-1238 (Mar. 1991).
Sato et al, High Jc Silver Sheathed Bi Based Superconducting Wires, IEEE Trans. on Magntics 27(2) 1231 1238 (Mar. 1991). *
The Internal Oxidation of Silver Alloys at High Pressures and in Atomic Oxygen D. St o ckel et al. AFSC Oxidation of Tengsten and other Refractory Metals, ML TR 64 162 (Apr. 1965). *

Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6393690B1 (en) * 1995-05-19 2002-05-28 American Superconductor Corpration Structure and method of manufacture for minimizing filament coupling losses in superconducting oxide composite articles
US6202287B1 (en) * 1996-01-18 2001-03-20 American Superconductor Corporation Method for producing biaxially aligned super conducting ceramics
US6448501B1 (en) * 1998-03-30 2002-09-10 Mcintyre Peter M. Armored spring-core superconducting cable and method of construction
US6311385B1 (en) * 1998-04-28 2001-11-06 Sumitomo Electric Industries, Inc. High temperature oxide superconducting wire and method of manufacturing thereof
US20030226677A1 (en) * 1999-09-07 2003-12-11 Utilx Corporation Flow-through cable
US20050006117A1 (en) * 1999-09-07 2005-01-13 Utilx Corporation Flow-through cable
US6743531B2 (en) * 2001-06-22 2004-06-01 Fujikura Ltd. Oxide superconducting conductor and its production method
US20030134749A1 (en) * 2001-06-22 2003-07-17 Fujikura Ltd. Oxide superconducting conductor and its production method
US20050079116A1 (en) * 2001-06-22 2005-04-14 Fujikura Ltd. Oxide superconducting conductor and its production method
US20080227245A1 (en) * 2002-01-02 2008-09-18 Samsung Electronics Co., Ltd. Thin film transistor array panel and a method for manufacturing the same
US20040238886A1 (en) * 2002-01-08 2004-12-02 Jae-Gab Lee Thin film transistor array panel and a method for manufacturing the same
US7375373B2 (en) * 2002-01-08 2008-05-20 Samsung Electronics Co., Ltd. Thin film transistor array panel
US7608494B2 (en) 2002-01-08 2009-10-27 Samsung Electronics Co., Ltd. Thin film transistor array panel and a method for manufacturing the same
US20070062713A1 (en) * 2005-09-12 2007-03-22 John Szurpicki Rotary lawn edger tool

Similar Documents

Publication Publication Date Title
US6444917B1 (en) Encapsulated ceramic superconductors
US6448501B1 (en) Armored spring-core superconducting cable and method of construction
US6428635B1 (en) Substrates for superconductors
US5232908A (en) Method of manufacturing an oxide superconductor/metal laminate
US5358929A (en) Method of joining superconducting wire using oxide high-temperature superconductor
US5929000A (en) Multifilamentary oxide superconducting wires
EP0282286A2 (en) Superconducting wire and method of manufacturing the same
EP0357779A1 (en) Superconductive wire and cable having high current density, and method of producing them
US4929596A (en) Process for producing a multiple-filament oxide superconductor
US4917965A (en) Multifilament Nb3 Al superconducting linear composite articles
US5122507A (en) Process for manufacturing a superconducting composite
US5908812A (en) Structure for hts composite conductors and the manufacture of same
WO1999017307A1 (en) Substrates with improved oxidation resistance
US5635456A (en) Processing for Bi/Sr/Ca/Cu/O-2223 superconductors
US4665611A (en) Method of fabricating superconductive electrical conductor
Suenaga et al. Superconducting properties of multifilamentary Nb3Sn made by a new process
US6038462A (en) Structure and method of manufacture for minimizing filament coupling losses in superconducting oxide composite articles
US4975416A (en) Method of producing superconducting ceramic wire
US3983521A (en) Flexible superconducting composite compound wires
US3930903A (en) Stabilized superconductive wires
US6370405B1 (en) Fine uniform filament superconductors
US5625332A (en) Oxide superconducting wire and superconducting apparatus thereof
US4224735A (en) Method of production multifilamentary intermetallic superconductors
US4330347A (en) Resistive coating for current conductors in cryogenic applications
Osamura et al. Effect of thermomechanical treatment on the critical current density of Ag-sheathed B (Pb) SCCO tapes

Legal Events

Date Code Title Description
CC Certificate of correction
FPAY Fee payment

Year of fee payment: 4

REMI Maintenance fee reminder mailed
LAPS Lapse for failure to pay maintenance fees
FP Expired due to failure to pay maintenance fee

Effective date: 20080523